This project is aimed at understanding the biochemical pathology of Batten disease (a devastating mental retardation syndrome), using lymphoblastoid cell lines and fibroblast cultures from patients and neural tissues cultures similar to those used in the other projects. In the infantile form (CLN1) we will focus on the substrate specificity on the defective palmitoyl: protein thioesterase, the storage material and the source of this storage material from neural membrane turnover. In the late infantile form (CLN2) we will focus on the substrate specificity of the defective pepstatin-insensitive carboxyl peptidase, the storage material and its source, and in the juvenile form (CLN3) we will focus on the possible role of the protein gene product in facilitating proteolysis in the lysosome.